1. Field
At least one example embodiment of the inventive concepts relates to data mirroring technology.
2. Description of the Related Art
For several decades, hard disk drives (HDDs) have been used as representative storage devices. An example of an HDD is a mechanical device that performs a read/write operation using the head of a disk that rotates at certain speed. The HDD may be relatively inexpensive in view of its capacity. However, since the read/write performance of the HDD is dependent on the rotating speed of the disk, the read/write performance, in particular, the random read/write performance of the HDD may be more limited than that of a semiconductor-based storage device. In addition, the HDD may have a higher breakdown rate than the semiconductor-based storage device. A breakdown in a storage device is detrimental because it can cause the loss of user data.
To overcome the limited performance and reliability of the HDD, redundant array of independent disks (RAID) technology has been widely utilized. The RAID technology forms an HDD array by connecting a number of HDD devices and appropriately distributes read/write operations among the HDD array. The RAID technology is classified into a number of detailed technologies—e.g., RAID 0 (striping), RAID 1 (mirroring), RAID 5 (striping with distributed parity), RAID 10 (mirroring and striping), etc.—according to the data arrangement policy between HDD devices. In particular, the mirroring technology may include storing the same data in two or more HDDs. Therefore, even if one of the HDDs breaks down, data loss can be prevented because an HDD which has not broken down can continuously provide data service.
Meanwhile, the utilization of solid state drives (SSDs) is continuously increasing. An SSD is compatible with an HDD and may have better performance and reliability than the HDD. Unlike the HDD, the SSD may have no mechanical device therein. Therefore, the SSD may have a lower breakdown rate than the HDD. Furthermore, the read/write performance, in particular, the random read/write performance of the SSD may be higher than that of the HDD. Although the SSD may be superior to the HDD in terms of performance and reliability, the RAID technology can also be applied to the SSD by forming an SSD array in order to achieve additional performance improvement or prevent data loss due to the breakdown of the SSD.